The refraction of the eye; including a complete treatise on opthalmometry; a clinical text-book for students and practitioners . Via. 17. 26 THE REFRACTION OF THE EYE the horizontal, is less curved, and consequently it is astig-matism against the rule. 5. Mixed astigmatism against the rule. — The vertical me-ridian is hypermetropic, focusses rays back of the retina, andis less curved than the horizontal meridian, which is myopic,and focusses rays in front of the Fig. 18. By the above diagrams we see that astigmatism may beagainst the rule in all its forms. So long as the vertical me-r
The refraction of the eye; including a complete treatise on opthalmometry; a clinical text-book for students and practitioners . Via. 17. 26 THE REFRACTION OF THE EYE the horizontal, is less curved, and consequently it is astig-matism against the rule. 5. Mixed astigmatism against the rule. — The vertical me-ridian is hypermetropic, focusses rays back of the retina, andis less curved than the horizontal meridian, which is myopic,and focusses rays in front of the Fig. 18. By the above diagrams we see that astigmatism may beagainst the rule in all its forms. So long as the vertical me-ridian of the cornea is less curved than the horizontal, that isastigmatism against the ride. I have gone very particularly and minutely into this pointof astigmatism with the rule and astigmatism against the rule,because I have found in my teaching at the Post-GraduateSchool of Medicine that it is a point on which most beginnersare in doubt. I may add that I have seen many others whohave used the instrument for a long time not clear on thequestion. Some authors are inclined to give but little impor-tance to it, but I have found it of much value in , if, on finding the astigmatism with or against therule with the ophthalmometer, you can teach the student to WHI THE MIRES OVERLAP AND SEPARATE 27 picture in his minds eye,* so to speak, the condition of cur-vature of the cornea and the position of the focal points of itstwo chief meridians of curva
Size: 1541px × 1622px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthordavisa, bookcentury1900, bookdecade1900, booksubjecteye
